Synchronous-motor-driven phonograph



Nov. 11, 1930. c. I. HALL 1,781,577

SYNGHRONOUS MOTOR DRIVEN PHONOGRAPH Filed Nov. 28, 1928 I 14 i 15 {'i 1512a I n 11 v o /4 v 2 1 g\ C ONSTANT FREQUENCY SOURCE Inventor:Chester- 1. H aLL', WW

H i s Attor'neg-.

' Patented Nov. 11, 1930 UNITED STATES PATENT orrlca cnns'rnn I. HALL,or roar WAYNE, INDIANA, assrenoa 'ro GENERAL ELECTRIC com- PAJS'Y,

A CORPORATION OF YORK SYNGHRONOUS-MOTOB-DRIVEN PHONOGRAPH Applicationfiled November 2 M invention relates to a synchronous mo tor ri've forphonographs and its primary object isto provide a simple yet reliableelectrically driven phonograph which requires no s eed governor.

T e usual phonograph drive requires some kind of a speed governorcontrolled brake to maintain the speed of the record turn table at thevalue required for correct sound reproduction. In spite of variousprecautions the usual speed governing mechanism tends to produceundesirable noises. This trouble is articularly noticeable in thosedrives which employ gearing between the driving motor and a rotatingpart upon which the brake operates due to the variation in powertransmitted therethrough under different braking conditions. I havefound that the elimination of the overnor and brake reduces undesirablenoises, simplifies the mechanism and reduces the cost withoutsacrificing reliability. When a'speed governor is employed, slightvariations in speed still exist because it requires a change in speed tochange the governor and brake setting before any regulation can takeplace. This slight variation in speed may be and often is greater thanthe variations in frequency of a well regulated alternating currentsystem. It is therefore feasible to eliminate the governor entirely anddrive the phonograph by a synchronous motor.

The power required to drive a phonograph at normal speed without a brakeis very small indeed and if we provide other means for bringing themotor and] turn table up to the operating speed a very small synchronousmotor may be employed. Consequently, I prefer to employ the very simplenon-sel starting synchronous motor and provide other means for bringingthe rotating parts up to speed. The preferred starting means comprises aspring operated device combined with the motor line switch and a brakefor stopping the turn table when the switch is opened.

The features of my invention which are believed to be novel andpatentable will be pointed out in the claims appended hereto.

For a better understanding of my invention, reference is made to thefollowing descripplace but shown a, 1928. Serial No. 322,497.

tion to the accompanying drawing in which Fig. 1 represents a plan viewof the synchronous motor drive and starting mechanism with parts brokenaway to better expose the invention. Fig. 2 shows a side view of themechanism of Fig. 1 with the turn table in in section; Fig. 3illustrates the simplicity of the preferred type of synchronous motoremployed to drive the phonograph; Fig. 4 represents a modification ofthe connection between fly wheel 18 and rotor 19; and Fig. 5 shows analternative starting arrangement.

Referring to Figs. 1 and 2, 10 represents a supporting framework whichwill ordinarily be enclosed in a cabinet, not shown. This frameworkcontains and supports the driving mechanism. The phonograph turn tableis shown at 12 and is suitably supported .in driving relation with andat the top of the drive shaft 13. Shaft 13 carries a gear H which mesheswith a worm gear 15 on the shaft 16 driven by the synchronous motor 17.The worm gear 15 is cut at such an angle that shaft 16 may be drivenfrom shaft 13 during the startin operation and for this purpose theteegi of worm gear 15 have an angle of pitch exceeding 45 degrees. Witha cycle four-pole synchronous motor operating at 1800 R. P. M., the gearratio between 15 and 14 will be in the neighborhood of 22 to 1 whichwill cause the turn table to operate at the normal honograph recordspeed in the neighb ood of R. P. M. The pole number of the motor andgear ratio may be changed as desired. Such a motor has a speed which isindependent of variations in temperature and in voltage.

Owing to chronous motor to hunt I prefer to fprovide a frictionalconnection between sha t 16 and the motor armature and to providesufficient flywheel effect in the shaft to prevent any possibility ofchattering at the gear reduction. To this end a flywheel 18 is securedto shaft 16 but the motor armature 19 is not directly fastened thereto.The armature 19 is provided with spring fingers 20 which are infrictional contact with the'adjacent end of the the tendency of a simplesynflywheel l8 and this frictional contact is maintained by a collar 21secured to shaft 16 on the opposite side of the-armature. frictionalclutch thus formed provides the The friction coupling may be replaced bya resilient spiral spring connection between flywheel resented at 20 inFig. 4.

I prefer also to provide a resilient pack ing such as felt or cork padsat the two ends of the shaft 16 to eliminate end play noises. Such padsare indicated at 21 o bearing cup 22 and a-steel ball 23 which restsagainst the end of the shaft. I have found that by adjusting the endwisedisplacement of the bearing cup 22 to maintain the pads under slightcompression, end play ment may be provided for and made between thesupporting frame and cup by loosening the fastening screw 22 shown inFig. 2.

Where the phonograph is started by hand so and where the motor is of thenon-self-starting type it may be of a very simple construction as shownin Fig. 3. The rotor may con sist simply of solid iron or other magneticmaterial and have the desired number of salient poles. The stator islikewise of sim le construction and does not require shading coils. Itis known that such a motor while non-sclf-staiting will operatesynchronousl when brought up'to its synchronous speed: Since the onlypower required of the motor is to operate the phonograph turn table atnormal speed it maybe very small and requires little energy. erence fora. non-self-starting synchronous motor I do not mean to limit myinvention Whether self-starting or non-selfstarting it will be apparentthat a synchronous motor will drive the stant speed when energized froma constant frequency source and that as a consequence the necessity of aspeed governor and brake is eliminated.

f a non-self-starting synchronous motor is usedit will be necessary tobring it up to greater than that required to drive the phonograph atnormal speed which is considerably less than that re uired for starting.One way of bringing t e motor up to speed is to simply give the turntable the required spin by hand. owever, a more exact and less crudemethod is desirable and the preferred 25 is leyer 29. Th

between the tension in spring 27 switch33 closed and pad 31.

By indicating my pref: 27

means for doing this, combined. with a. motor switch and a turn tablestopping brake, will now be described.

The top bearin housing for shaft 13 is indicated at 24. n the upper endof this housing an arm 25 is pivoted. The outer end of this arm extendsslightly beyond the turn table and cooperates with a latch 26. A siiral' spring 27 has its inner end fastened to t outer end secured to apin in the lower side of arm 25. Pivotally mounted at e outer end ofLever 29 is normally biased to the shown in full lines with the pad'30against the inner rim of the turn table by a spring 34. .owever, whenthe part 32 strikes against the switch contacts, lever 29 istnrned aboutpivot '28 in a clockwise direction a slight amount until arm 29'comesagainst a stop such as a stop is operation from the mm 31 and the desufiicientto hold 31 away from rim The position of the parts as shown infull lines is the position when the phonograph is not in use, the motorcircuit is open, the turn table is braked at 30,; and the spring isunder tension. When it is desired to start thephonograph, latch 26 ismoved to release lever 25. Arm 25 moves in a clockwise direction, itbeing driven ad 30 is in contact with the turn table and the turn tabletogether with all rotating parts e tension of spring 27 is suflicient toaccelerate the rotatable parts of the drive to 'approximately'the normaloperating speed during the movement of arm 35 to the position shown indotted lines. When the arm reaches therunning'position, brake pad 30 isquickly moved from the rim of tacts to open, brakes the winds springe'stationary bearing housing and its 75 desired, the position of thecatch 26 may be made adjustable about the periphery of the turn tablefor the purpose of adjusting the accelerating impulse given to rotatingparts. The arm 25 and the parts carried thereby are preferably made aslight as practicable while the support for switch 33 has sufficientresiliency to stop the arm 25 without shock.

Fig. 5 represents an alternative arrangement for starting the apparatus.The arm 25-, the spring 27 and the motor contacts 33 are substantiallyas However, instead of a friction contact at the rim of the disc, I haverepresented a ratchet wheel 36 on the shaft 13 and a pawl lever 37 onarm 25 which is arranged to engage and drive the ratchet wheel 36 whenthe arm 25 is drawn back and released as explained in connection withFig. 1. As the parts approach the switch contacts 33 the pawl 37 isthrown outward by'the cam shaped finger 38 on the contact. The motorcircuit isthus closed and spring 27 holds it closed by pressing arm andpawl 37 towards the switchcontacts. In accordance with the provisions ofthe patent statutes I have described the principle of operation of myinvention, together with the apparatus which I now consider to representthe best embodiment thereof; but I desire ratus shown and described isonl tive and that the invention may h illustrae carried out by othermeans.

motor for driving What I claim by Letters Patent of the United Statesis:

1. In a phonograph drive, a shaft, a record turn table mounted on saidshaft, a gear on said shaft, a second shaft, a synchronous the saidsecond shaft, a worm gear on said second shaft meshing with the firstmentioned gear, the pitch of said worm being such that the motor may bestarted through said gears by rotation of the turn table.

2. In a phonograph drive a turn table shaft provided with a gear, asecond shaft carrying a worm meshing with said gear, a flywheel on thesecond mentioned shaft, a synchronous motor for driving said shaft, anda driving connection permitting relative movement between saidsynchronous motor and said second shaft, said connection and flywheelserving to prevent hunting pulsations of said synchronous motor frombeing transmitted through said gears.

3. A phonograph drive comprising a phonograph record turn table, asynchronous motor for driving said turn table, a starting arm for saidturn table and motor pivoted on the axis of rotation of said turn table,a spring tending to turn said arm in the normal direction of rotation ofsaid turn table, a normally open switch for said moand to serve and afriction brake tor positioned to be closed by as a stop for said arm,

represented in Fig. 1.

to have it understood that the appaas new and desire to secure for saidturn table carried by said arm and arranged to be released fromengagement with said turn table by movement of said arm into engagementwith said switch.

4. A phonograph motor drive comprising in combination with a record turntable a synchronous motor for driving said turn table, starting meansfor said turn table comprising an arm pivoted on the axis of rotation ofthe turn table, a spring for turning said arm in the normal direction ofrota-,

tion of said table, a catch cooperating with the outer end of said aimand adapted to hold the arm against rotation with the spring undertension, a lever pivoted on said arm and carrying a friction pad adaptedto engage in driving relation with a rotatable portion of thephonograph, a switch for said motor having normally open resilientcontacts positioned to be engaged and closed by said lever when said armis released and allowed to rotate under the action of said spring, saidcontacts serving to release said. lever from said driving engagement.

In witness whereof, I have hereunto set my hand this 26th day ofNovember, 1928.

CHESTER I. HALL.

